This new API will write the function filters into the
set_ftrace_filter file.
tracefs_function_filter()
https://bugzilla.kernel.org/show_bug.cgi?id=210643
Signed-off-by: Sameeruddin shaik <sameeruddin.shaik8@xxxxxxxxx>
diff --git a/include/tracefs.h b/include/tracefs.h
index f3eec62..a2249d0 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -50,6 +50,7 @@ int tracefs_trace_on(struct tracefs_instance *instance);
int tracefs_trace_off(struct tracefs_instance *instance);
int tracefs_trace_on_fd(int fd);
int tracefs_trace_off_fd(int fd);
+int tracefs_function_filter(struct tracefs_instance *instance, const char **filters, const char *module, bool reset, const char ***errs);
/**
* tracefs_trace_on_get_fd - Get a file descriptor of "tracing_on" in given instance
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index e2dfc7b..4e168df 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -18,6 +18,7 @@
#include "tracefs-local.h"
#define TRACE_CTRL "tracing_on"
+#define TRACE_FILTER "set_ftrace_filter"
static const char * const options_map[] = {
"unknown",
@@ -387,3 +388,96 @@ void tracefs_option_clear(struct tracefs_options_mask *options, enum tracefs_opt
if (options && id > TRACEFS_OPTION_INVALID)
options->mask &= ~(1ULL << (id - 1));
}
+
+static int controlled_write(const char *filter_path, const char **filters, const char *module, bool reset, const char ***errs)
+{
+ int flags = reset ? O_TRUNC : O_APPEND;
+ int write_size;
+ char *each_str;
+ int ret = 0;
+ int j = 0;
+ int size;
+ int slen;
+ int fd;
+ int i;
+
+ fd = open(filter_path, O_WRONLY | flags);
+ if (fd < 0)
+ return 1;
+
+ for (i = 0; filters[i]; i++) {
+ slen = strlen(filters[i]);
+ if (!slen)
+ continue;
+
+ if (module)
+ /* Adding 5 extra bytes for ":mod:"*/
+ slen += strlen(module) + 5;
+
+ /* Adding 2 extra byte for the space and '\0' at the end*/
+ slen += 2;
+ each_str = calloc(1, slen);
+ if (!each_str)
+ return 1;
+ if (module)
+ write_size = snprintf(each_str, slen, "%s:mod:%s ", filters[i], module);
+ else
+ write_size = snprintf(each_str, slen, "%s ", filters[i]);
+
+ size = write(fd, each_str, write_size);
+ /* compare written bytes*/
+ if (size < write_size) {
+ if (errs) {
+ errs[j++] = &filters[i];
+ ret -= 1;
+ }
+ }
+ free(each_str);
+ }
+ errs[j] = NULL;
+ close(fd);
+ return ret;
+}
+
+/**
+ * tracefs_function_filter - write to set_ftrace_filter file to trace particular functions
+ * @instance: ftrace instance, can be NULL for top tracing instance
+ * @filters: An array of function names ending with a NULL pointer
+ * @module: Module to be traced
+ * @reset: set to true to reset the file before applying the filter
+ * @errs: A pointer to array of constant strings that will be allocated
+ * on negative return of this function, pointing to the filters that failed.
+ * May be NULL, in which case this field will be ignored.
+ *
+ * The @filters is an array of strings, where each string will be used to set
+ * a function or functions to be traced.
+ *
+ * If @reset is true, then all functions in the filter are cleared before
+ * adding functions from @filters. Otherwise, the functions set by @filters
+ * will be appended to the filter file
+ *
+ * returns -x on filter errors (where x is number of failed filter srtings)
+ * and if @errs is not NULL will be an allocated string array pointing to the
+ * strings in @filters that failed and must be freed with free().
+ *
+ * returns 1 on general errors not realted to setting the filter.
+ * @errs is not set even if supplied.
+ *
+ * return 0 on success and @errs is not set.
+ */
+int tracefs_function_filter(struct tracefs_instance *instance, const char **filters, const char *module, bool reset, const char ***errs)
+{
+ char *ftrace_filter_path;
+ int ret = 0;
+
+ if (!filters)
+ return 1;
+
+ ftrace_filter_path = tracefs_instance_get_file(instance, TRACE_FILTER);
+ if (!ftrace_filter_path)
+ return 1;
+
+ ret = controlled_write(ftrace_filter_path, filters, module, reset, errs);
+ tracefs_put_tracing_file(ftrace_filter_path);
+ return ret;
+}
--
2.7.4
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